Although ebooks appear relatively simple on their surface, there’s a lot going on under the hood that authors new to the indie publishing game may not be aware of. Ebooks behave fundamentally different than the documents you’re probably used to working with (like Microsoft Word documents or PDFs). One of the first lessons authors learn is that there are multiple formats for ebooks, and not every retailer accepts every kind of file for sale.
So, which ebook formats do you need to cover all of your bases?
Luckily, it’s not too complicated. The short answer is that you’ll want two files: an EPUB and a MOBI. Those two files will cover you for virtually every online retailer. That should be your goal: coverage. The more channels your book is available through, the better overall results you’ll see.
Let’s break it down further.
A crash course in EPUB:
EPUB (or ePub) is short for “electronic publication” and was developed as an open-source standard by the International Digital Publishing Forum. It is by far the most common ebook format, and it’s sold by every major ebook retailer except one: Amazon. It’s the native file type of iBooks, Nook, and Kobo, to name but a few.
The capabilities of the EPUB format are constantly evolving, and as e-reader devices (iPads, Nooks, etc.) update their software, new functionality becomes possible over time. In the last few years, one of the biggest of these developents has been support for Fixed-Layout EPUBS.
Reflowable vs. Fixed-Layout EPUBs:
Standard ebooks are reflowable, meaning your e-reader pulls the text from the files and “flows” it across pages differently based on your font settings, zoom, the size of the screen in question, etc., allowing the book to look good regardless of the specific device and the customer’s front preferences.
Fixed-layout EPUBs preserve all the formatting of the book across devices, meaning every page is the same no matter what device you’re reading on, and they offer better control of the placement of items on the page. This can enable the kinds of dramatic, creative layout options that you’re used to seeing in print. However, readers won’t be able to change the font and zoom settings; constructing these books are more complex and time-consuming, and not all e-readers will even handle them properly. As a result, they tend to be more expensive to produce. They’re a good choice when formatting is the highest priority–such as with children’s books. For most books, however, the safest route is reflowable.
A crash course in Mobi:
Things get harder to keep track of with Kindles. The file you’re likely to upload to Amazon for your Kindle customers is a .mobi, developed originally by the French company Mobipocket. It’s difficult to safely edit the contents of a .mobi file after it’s been produced, so many ebook designers–including those at BookFuel–initially construct your ebook as an EPUB, then convert from there to a Mobi file. When using Amazon’s own conversion software, a .mobi file is what’s produced.
You may be aware of KF8 (Kindle Fire 8), the more robust file type Amazon started using with the Kindle Fire. KF8 adds support for many more formatting options (including fixed-layout files), and it’s really not much more than an EPUB file wrapped in some of Amazon’s own code. Modern Kindle ebook files actually contain both Mobi and KF8 databasses within the same file–so while your Kindle ebook may have a .mobi file extension, you can rest assured that you’re still getting all the features KF8 allows.
What about PDFs?
Prior to the popularization of e-readers, PDF ebooks were commonly sold on the Internet. Since the content of a PDF is the same across multiple computers (the fonts, images, etc. are all embedded in the PDF itself), it made them the strongest option for preserving the look of a book. Most e-readers do read PDFs, though they might recognize them as “documents” as opposed to “books.” This is because they don’t have any of the functionality of modern ebook files. As such, they’re not commonly sold via online retailers anymore.
The long and short of it: Get a .epub and a .mobi and call it a day. Between the two files, you’re covered.